The McArdle Electron Microscopy Facility has been supported in part by the CCSG for over 30 years. For the next grant period we are consolidating several resources related to light microscopy with this facility (renamed the Microscopy Facility) to improve their upkeep and facilitate training of students and fellows in their use. This is appropriate since the expertise needed for electron microscopy and its interpretation overlaps with that for light microscopy. The two goals of the Electron Microscopy component, which is located in a 300 square foot laboratory basement of McArdle, are: (1) to provide basic electron microscopy services to all research groups in the McArdle Laboratory; (2) to perform collaborative studies with principle investigators and their graduate students and postdoctoral fellows. Having a self sufficient transmission microscopy facility located in the McArdle Laboratory (in the basement) permits easy access to all faculty members and is essential to instructing graduate students in the basic principles of electron microscopy. The facility contains a Hitachi H-7000 electron microscope, a new Reichart Ultracut E and two Sorvall MT-2 ultramicrotomes, a Denton vacuum evaporator, and darkroom facilities for developing negatives and making prints with a state-of-the-art print processor. Facilities for visible light and fluorescence microscopy are located in a 200 square foot laboratory on the 3rd floor of McArdle. The instrumentation includes a Zeiss Axiophot which is capable of a variety of different types of light microscopy as well as photomicroscopy. In addition, a Leitz research microscope with fluorescence and photomicrographic capabilities is available in the unit for general use. Images may be documented through the use of standard film cameras attached to the microscope or a CCD CAMERA, allowing later computer analysis of digital images.